Reverse order diagnosis

Other tools you will need for HPLC are fairly standard for a lab with a few exceptions. I keep two of the small open wrenches supplied with an HPLC system or a column for use with compression fittings, 1/4-in, a 5/8-in box wrench, and a 6-in crescent wrench for column work, a file, a Terry tool tubing cutter, a couple of pairs of blunt nose pliers for tube flexing during cutting, a reversible screw driver, a jeweler s screwdriver for phoenix block s screws, a universal Allen wrench set, an adjustable-head dental mirror (for seeing behind boxes to hook up leads), and a stopwatch for timing flow. The key is to lock up your tool kit to prevent tool evaporation. 

Spare parts that are needed are compression fittings and ferrules, plunger and injector rotor seals, an extra plunger and seals, column filters, and injector needle port seals. If you do not use pacification, you might want to keep a set of check valves on hand. I always have one coil each of 0.01- and 0.02-in tubing in addition to my column blank. A replacement solvent inlet line with a porous stone is useful in case of corrosion. If you filter solvents, you need cellulose, nylon, and Teflon filters. You also need a back-up lamp for your detector. 

If it takes a while to get replacements, double the amounts of the preceding parts and add a detector flow cell, another Ci8 column, and a full pump head. If you are going to Antarctica for the season, an extra injector, pump, detector, strip chart recorder, and a case each of strip chart paper and pens might be nice. One of my customers found that his back-order time in Little America (Antarctica) was 14 months. 

The most commonly reported symptom of a bad system is baseline drift the second is a noisy baseline. Baselines that drift up and down are almost always due to peaks coming off the column. Baselines that drift up continuously can be garbage, a bad detector lamp, or decomposition on the flow cell window. Noise can come from almost anywhere in the system. 

When you have a problem, do not guess as to where it might be. Start looking for problems from the strip chart end of the system. Prove that the strip chart is good, then use it to check the detector, and use the detector to check the injector and finally the pump. Using this systematic, reverse-order analysis will save you time and frustration. 

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You now have the tools to find most of the problems in the system. Remember that 80% of the problems are column problems and about 60% of those come from dirty water. If the problem fails to leave with removing the column and putting in a column blank, then do reverse-order diagnosis. It will be amazing how much time you save. 

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